Locking assembly for chair



Sept. 15, 1964 B. B. JUNKUNC LOCKING ASSEMBLY FOR CHAIR Filed March 8, 1962 Sept. 15, 1964 B. B. JUNKUNC LOCKING ASSEMBLY FOR CHAIR Filed March 8, 1962 3,148,854 LGQKEJG ASEMELY FGR CHATR Bela B. .l'unlrunc, 1087i Prospect, Chicago, Ell. Filed 8, 1962, Ser. No. 178,448 8 Claims. (Cl. 2-i-S157) This invention relates to adjustable length devices, particularly to such a device used for adjusting the height of an article of furniture.

Furniture, such as chairs and tables that are used in schools, must be suitable to accommodate children of different sizes who for all intents and purposes fall into various age groups. The numbers in the various groups may fluctuate greatly during succeeding years and thus schools, must be suitable to accommodate children of difof desks and chairs in each size range to handle the maximum number of children they expect in each group. The leg heights of chairs for the different age groups vary between ten and eighteen inch heights, and the leg heights for desks vary between twenty and thirty inch heights. This problem is particularly acute today since the constantly shifting population makes accurate predicting very difficult. It can be appreciated that a device for adjusting the heights of school desks and chairs could result in substantial savings.

While devices for adjusting the heights of chairs and desks are not broadly new, those in present use have been found to be too expensive for general use on school furniture. The quantities of these items that are purchased make it mandatory that an adjusting device to be acceptable would have to be simple in design, efficient in operation, and low in cost. The devices should also be generally tamperproof to prevent school children from constantly changing their setting. By providing such an adjustment, the chair and desk inventory problem would be substantially eliminated, since the desks and chairs are usable for all age groups. In the case of chairs, it would only be necessary to stock two or three different seat sizes to accommodate wide ranges of groups.

In accordance with applicants invention, there is provided a simple yet highly efficient mechanism for varying the height of a chair or desk over the desired range. This mechanism is concealed so as to make it inaccessible to children to prevent unauthorized adjustment of the chair or desk height.

\Vhile the description contained hereinafter is directed to a chair, it is obvious that this mechanism could be applied to the legs of a desk or other items where it may be desirable to periodically adjust the height thereof.

In the instant case, the height of the chair is adjusted by providing vertically aligned releasably engaged telescoping tubes. One of the tubes is secured to the seat frame and the other is secured to the base support or leg frame of the chair. The telescoped end of the inner of the two telescoping tubes is slit and releasable and adjustable locking means are moved into and out of engagement with the slit end of the inner tube to move the inner tube into and out of tight frictional contact with the outer tube. The adjusting mechanism for the locking means is concealed so that it is necessary to turn the chair over to release the locking means to vary the height of the chair. Appropriate indicia are marked on the tubes to indicate the height at which the seat of the chair is set.

Other features and advantages will be apparent from the following specification when taken in conjunction with the accompanying drawings, in which:

FIGURE 1 is a side elevation view of a chair embodying the invention;

FIGURE 2 is a view taken along lines 2-2 of FIG- URE 1;

FIGURE 3 is an enlarged cross-sectional View taken along lines 3-3 of FIGURE 1;

United states Patent 3 l 43 ,351 Patented Sept. 15., '1 964 FIGURE 4 is a partial sectional view of the telescoping tubes; and

FIGURE 5 is a cross-sectional View taken along lines 5-5 of FIGURE 3.

Referring first to FIGURE 1, there is illustrated a chair comprising a leg frame 1 and a seat frame 2. The leg frame includes a pair of transversely spaced tubes 3 formed in the shape of an inverted U to define front legs 4 and rear legs 5. The front legs and rear legs of the tubes are interconnected by braces (not shown) for providing lateral support for the leg frame. Extending between the horizontal portions of tubes 3 are a second pair of transversely extending braces 8. These braces serve as an additional support for the leg frame and as a support for a pair of horizontally extending vertically spaced plates 9, it). These plates 9, it support a depending tube 11 having a. rectangular cross-section (see FIGURES 3 and 5). The depending tube 11 receives a rectangular tube 12 secured to the underside of the seat frame for supporting same in a manner described below.

The seat frame 2 includes a horizontally extending tubular frame portion having horizontally extending parallel arms 1%, 17 which support a seat 18. The seat is releasably secured to the arms 16, 17 and may be readily removed and replaced with a seat of a different size. The arms 15, 17 are interconnected by a vertically extending brace 19 for supporting the seat back rest 21. Between the arms 16, 17 are a pair offspaced rods 22 (see FIGURE 2) that support horizontally disposed parallel plates 23, 2d. Theplates 23, 24 suppot a vertically depending rectangular tube 12 that has outside dimensions that are slightly less than those of tube 11 so that the tube 12 slidably fits within the tube 11.

The relative position between the tubes 11, 12 determines the spacing between the leg and seat frames and thus the height adjustment of the seat. The range of adjustment of the height of the chair seat is determined by the axial lengths of the elescoped portion of tube 12. Thus, if a height variation of ten inches is desired, tube 12 would be longer than ten inches by an amount necessary to insure that seat frame 2, when moved to the maximum height will be solidly supported by leg frame 1. Tube 12 may be marked with appropriate markings to tell at a glance the height to which the seat has been adjusted.

Turning now to FIGURE 3, there are illustrated the details of the novel adjusting device which provide for the adjustability of the chair height and for releasably locking the seat frame in position after the seat has been moved to the desired height. As disclosed therein, the tube 12 has longitudinally extending slits 12a cut in its sides. As illustrated, these slits extend along substantially the full length of tube 12 so that the tube takes h form of a pair of parallel, opposed channels. If desired, these slits may extend along only that portion of the tube that is in telescoping engagement with tube 11. The slits are provided so that the portions of the tube between the slits can be expanded into tight frictional engagement with the inner surface of tube 11. Tube 12 is also provided with inwardly extending abutments or wedge followers 12b, 120, for reasons to be discussed hereinafter.

The expansion of the sides of tube 12 into engagement with tube 11 is accomplished by an adjustable locking mechanism 26 located substantially therein. After the chair height is selected, the locking mechanism forces the slit end of tube 12 outwardly into tight frictional engagement with tube 11 over a substantial portion of the length thereof to prevent relative movement therebetween.

The locking mechanism 26 consists of a locking bolt 27 and a pair of tapered plugs or wedges 28, 219. The bolt 27 extends through an enlarged opening 29a in plug 3 29 and into threaded engagement with plug 28. The plug 29 is supported by bolt head 27b. The tapered plug 28 has its narrow end in engagement with abutment 12b, and tapered plug 29 has its narrow end in engagement with abutment 12c.

The tapered plugs have a rectangular cross-section and the dimensions of the plugs at'their wider ends are slightly less than the inner dimensions of tube 12. This relationship between the plugs and tube 12 prevents relative rotation between the plugs and tube. With the foregoing relationship between the bolt 27 and tapered plugs, rotation of bolt 27 in one direction will force threaded plug 28 downwardly into wedging engagement with abutment 12b, and will also force plug 29 upwardly into wedging engagement with abutment 12c. The wedging action of these plugs moves the slit portion of tube 12 into tight frictional engagement with tube 11. Opposite rotation of bolt 27 moves plug 28 upwardly away from abutment 12b and permits plug 29 to move downwardly away from abutment 120. The tight frictional engagement between the tubes is relieved, which allows the tubes to be moved relative to each other to readjust the height of the chair.

From the foregoing it will be observed also that by utilizing upper and lower wedge actions in the slit portion of the inner tube or opposed channels, a multiple locking and interfacial frictional locking is achieved over substantially the full length of the telescoped portions of the tube, at least between the abutment or wedge follower areas thereof.

It is to be noted that the particular configurations of the telescoped tubes and tapered plugs are intended to be illustrative only. It is desirable that the tubes 11, 12 and the plugs have a non-circular cross-section, but a circular configuration could be employed if other means were provided to prevent relative rotation between these parts. The non-circular or polygon shape has an advantage in that it will prevent rotation of the seat frame relative to the leg frame and unauthorized release of the locking engagement between the tubes. This arrangement also prevents a student from turning the seat and thus distracting the attention of other students in the class.

Also, the bolt and plug assembly could be replaced with a stud having rightand left-hand threads at its opposite ends on which the tapered plugs would be threaded. Other modifications could be employed without departing from the scope of the present invention. Furthermore, the particular chair frame structure is merely representative of numerous designs that could be used.

I claim:

1. A locking assembly for telescoping tubes comprising an outer tube, an inner tube in sliding engagement with said outer tube, the portion of said inner tube movable into said outer tube having longitudinal slits in opposite walls thereof to provide separable longitudinal portions, a pair of longitudinally spaced projections extending inwardly from each of said separable portions, a pair of longitudinally spaced tapered plugs having their narrow ends in cooperative engagement with said projections, and adjustable means for moving said plugs to expand said inner tube into frictional engagement with said outer tube to releasably lock. the telescoped tubes against sliding movement relative to each other.

2. An article of furniture comprising a top member, a base member, an inner tube and an outer tube in telescoping engagement, one of said tubes secured to the top member and depending from the underside thereof, and the other tube secured to said base member, the telescoped portion of said inner tube having separable longitudinal portions at its free end and a pair of longitudinally spaced projections extending inwardly from each of said separable portions, a pair. of longitudinally spaced tapered plugs having their narrow ends in cooperative engagement with said projections and adapted to expand the telescoped end of said inner tube to releasably lock the tubes against sliding movement relative to each other, and adjustable means operatively connected to said plugs for tightening and loosening them relative to the inner tube whereby the height of the top member may be readjusted.

3. An article of furniture comprising a top member, a base member, a polygonal inner tube and a polygonal outer tube in telescoping engagement, one of said tubes secured to and depending from said top member and the other tube secured to said base member, the inner end of said inner tube being slit, a first polygonal shaped tapered plug in said inner tube having its narrow end in wedging engagement with the slit portion of said inner tube, a second tapered plug in wedging engagement with the free end of said inner tube, and adjustable means cooperatively connected to said tapered plugs to move said plugs with respect to said slit end to tighten and loosen said slit end to releasably lock the inner tube relative to the outer tube when the top member is at a preselected height, the adjustable means being located within said outer tube whereby the adjusting means is substantially tamperproof.

4. A chair comprising a seat frame, a leg frame, an inner tube and an outer tube in telescoping engagement, one of said tubes depending from the underside of said seat frame and the other of said tubes secured to said leg frame, the inner end of said inner tube being slit to form separable longitudinal portions, a pair of longitudinally spaced projections extending inwardly from each of said separable portions, a pair of longitudinally spaced tapered plugs having their narrow ends in wedging engagement with said longitudinally spaced projections and adapted to expand said inner tube into frictional engagement with the outer tube, and adjustable means operatively connected to said plugs for tightening and loosening them relative to the inner tube whereby the height of the seat frame may be readjusted. a

5. A chair comprising a seat frame, a leg frame, an inner and an outer polygonal tube in telescoping engagement, one of said tubes depending from the underside of *said seat frame and the other tube secured to said leg frame, the telescoped portion of said inner tube being slit to form separable longitudinal portions, a pair of longitudinally spaced projections extending inwardly from each of said separable portions, a first polygon shaped tapered plug disposed within said inner tube and having its narrow end in \vedging engagement with one projection of each of said pairs of projections, and a second tapered plug longitudinally spaced from the first plug and having its narrow end in wedging engagement with the other projections of each of said pairs of projections to bias the telescoped portion of the inner tube into frictional engagement with the outer tube, and adjustable means including a rod in threaded engagement with said first plug to move the tapered plugs into and out of wedging engagement with the inner tube to permit regulation of the height of the chair.

6. A chair as set forth in claim 5 in which the rod has a head and the second plug is slidably disposed on said rod with the wider end of said second plugs juxtaposed against said head.

7. A chair comprising aleg frame, a vertically extending polygonally shaped outer tube secured to said frame, a seat frame, an inner polygonal tube extending from the underside of said seat frame into telescoping engagement with said outer tube, the telescoped portion of said inner tube being slit, a first polygonal tapered plug dis posed within the slit portion of said inner tube and having its narrower end in cooperative engagement therewith, a second polygon shaped tapered plug longitudinally spaced from said first plug and having its narrower end in engagement with said inner tube, a bolt having a head supporting said second plug and a threaded shank extending through an opening defined by said second plug and in threaded engagement with said first plug, the head of said bolt disposed within said outer tube and thus only accessible when the chair is oventurned to move said plugs into and out of engagement with said slit end to tighten and loosen the inner tube relative to the outer tube when the height of the chair is to be readjusted.

8. An article of furniture comprising a top member, a base member, a pair of telescopically arranged tubes including an inner tube and an outer tube, one of said tubes secured to and depending from said top member, the other of said tubes secured to and extending upwardly from said base member, said tubes being non-circular in cross section and interengaged to prevent relative rotation thereof, the inner end of said inner tube being slit,

a non-circular tapered plug engaging said inner tube at 15 2338783 the slit end thereof, the narrow end of said plug disposed in Wedging engagement with the slit portion of said inner tube, and adjustable means cooperatively connected to said plug to move said plug inwardly and outwardly with respect to said slit end of said inner tube to tighten and loosen said slit end in releasably locking engagement with said outer tube to adjustably dispose said top member at selected distances from said base member.

References Cited in the file of this patent UNITED STATES PATENTS 773,241 Wilton Oct. 25, 1904 2,291,748 'Neuwirth Aug. 4, 1942 Romeo Jan. 11, 1944 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 148 854 September l5 19b! Bela B. Junkunc It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1, line 15, strike out ",must be suitable to accommodate children of dif-" and insert instead are normally required to keep a large inventory column 2, line 30, for "suppot" read support line 38, for "elescoped" read telescoped Signed and sealed this 26th day of January 1965.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Ancsting Officer Commissioner of Patents 

1. A LOCKING ASSEMBLY FOR TELESCOPING TUBES COMPRISING AN OUTER TUBE, AN INNER TUBE IN SLIDING ENGAGEMENT WITH SAID OUTER TUBE, THE PORTION OF SAID INNER TUBE MOVABLE INTO SAID OUTER TUBE HAVING LONGITUDINAL SLITS IN OPPOSITE WALLS THEREOF TO PROVIDE SEPARABLE LONGITUDINAL PORTIONS, A PAIR OF LONGITUDINALLY SPACED PROJECTIONS EXTENDING INWARDLY FROM EACH OF SAID SEPARABLE PORTIONS, A PAIR OF LONGITUDINALLY SPACED TAPERED PLUGS HAVING THEIR NARROW ENDS IN COOPERATIVE ENGAGEMENT WITH SAID PROJECTIONS, AND ADJUSTABLE MEANS FOR MOVING SAID PLUGS TO EXPAND SAID INNER TUBE INTO FRICTIONAL ENGAGEMENT WITH SAID OUTER TUBE TO RELEASABLY LOCK THE TELESCOPED TUBES AGAINST SLIDING MOVEMENT RELATIVE TO EACH OTHER. 